Well, all it says that you shouldn't promote it on the "official channels" (i.e. the mailing list and the #guix libera.chat channel). Guix, the package manager itself, does not make installing non-free packages any more difficult than free packages. I suppose it could be said that Guix (the project) makes finding non-free packages harder, although anecdotally I will say that nonguix is the first thing I've heard about guix, since it seems to be the most controversial part of it.
While it's technically correct to say that the software itself does not make it particularly difficult to install non-free packages, it also doesn't come with non-free repos when you set it up, and the documentation and official support channels intentionally lack information on non-free repos. As default settings and documentation are a critical part of a software project, it still has the end result of making it harder (much harder for non-technically-inclined users) to do so.
